782 TRANSMISSION 



j 



in general to poisons of all sorts gradually administered, is 

 well known. 1 



So far as we are able to judge, immunity to infectious diseases 

 is produced in the same way. One attack of certain diseases 

 serves to render the individual immune through life. The 

 question that interests us at this point is this : Is this immunity 

 in any sense, or to any degree, transmitted to the descendants f 



It is claimed by some that if a sow recovers from a case of 

 hog cholera suffered while carrying young, the pigs will be born 

 with a high degree of resistance, if not absolute immunity ; the 

 idea being that they acquired in utero from the blood serum of 

 the mother the same kind of immunity that could be produced 

 by inoculation. 



There is too little experimental evidence as yet, and we know 

 too little of the real nature of acclimatization, to warrant positive 

 conclusions. What is known, however, is sufficient to raise some 

 interesting and exceedingly suggestive questions. 



If immunity can be produced in the mother by the repeated 

 injection of the chemical products of disease, and if such im- 

 munity be permanent, then why should not the young, whose 

 blood serum is derived from the mother, be also of the same 

 character? Whence come our " natural immunes " ? are they 

 mutants, or are they the products of immunizing influences 

 from the parentage ? Recent investigations seem to indicate 

 specific qualities in blood serum, 2 and it may very well be 

 that " blood relationship " means more than we have hitherto 

 supposed. 



To what extent immunity is purely a chemical question, and 

 to what extent it is connected with the power of the white 

 corpuscles to attack and digest invading organisms, we do not 

 know. In so far as it depends upon or affects the serum of the 

 blood it may well be a transmissible quality from the female 

 mammal if not from other parents. 



1 C. B. Davenport, Experimental Morphology, Part I, pp. 28-32 ; Vernon. 

 Variation in Animals and Plants, pp. 386-387. 



2 When the blood serum of one species is injected into the veins of another, 

 the most injurious effects are said often to follow, and the so-called precipitin 

 test seems to establish the fact that differences in blood serum of different species 

 are profound. See Blood Immunity and Blood Relationship, by Nuttall, reviewed 

 in Science, October 28, 1904. 



